Phospholipids inDrosophila heads: Effects of visual mutants and phototransduction manipulations

Abstract

A procedure was developed to label phospholipids in Drosophila heads by feeding radioactive phosphate (32Pi). High-performance thin-layer chromatography showed label incorporation into various phospholipids. After 24 h of feeding, major phospholipids labeled were phosphatidylethanolamine (PE), 47%; phosphatidylcholine (PC), 24%; and phosphatidylinositol (PI), 12%. Drosophila heads have virtually no sphingomyelin as compared with mammalian tissues. Notable label was in ethanolamine plasmalogen, lysophosphatidylethanolamine, lysophosphatidylcholine and lysophosphatidylinositol. Less than 1% of the total label was in phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate. Other lipids labeled included phosphatidylserine, phosphatidic acid and some unidentified lipids. A time course (3-36 h) study revealed a gradual decrease in proportion of labeled PI, an increase in proportion of labeled PC and no obvious change in labeled PE. There were no significant differences in phospholipid labeling comparing the no receptor potential (norpA) visual mutant and wild type under light vs. dark conditions. However, overall 32P labeling was higher in the wild type fed in the light as compared to the dark and to norpA either in light or dark. This suggests that functional vision facilitates incorporation of label. Differences in phospholipid labeling were observed between young and aged flies, particularly in lysophospholipids and poly-PI, implicating phospholipase A2 function in recycling. v Manipulations such as the outer rhabdomeres absent and eyes absent mutants and carotenoid deprivation failed to yield notable differences in phospholipid labeling pattern, suggesting that phospholipids important to vision may constitute only a minor portion of the total labeled pool in the head.

Towards a membrane proteome in Drosophila: a method for the isolation of plasma membrane

“…In order to increase our PM yield, we decided to test the effect of various PEG/Dextran concentrations on the partitioning of the marker proteins for the PM and ER (Figure 5). Since the spectrum of membrane lipids in vertebrates and invertebrates are significantly different [29-31], the optimal concentrations of PEG and Dextran for 2PAP derived for vertebrate analyses may well be inappropriate for invertebrates. Moreover, because we are pre-enriching for PM through the use of a density gradient we need be less concerned about differential partitioning of PM from endomembane based upon their relative solubility in the PEG and dextran phases.…”

“…In contrast, intracellular compartments have a higher percentage of phosphatidylcholine and phosphatidylethanolamine, much-reduced sphingomyelin and phosphatidylserine, and much lower cholesterol levels ( ibid ). Whereas, plasma membranes from Drosophila contain similar lipid head groups to vertebrates, they have shorter fatty acid chains [30,31], and the major sterol is ergosterol [30]. We have found no reports comparing the lipid profile of PM and intracellular membranes in Drosophila ; however, a study on mosquito Aedes aegypti (also of the order Diptera ), suggests that sphingosine containing lipids are not significantly enriched in the PM, nor are phosphatidylcholine and phosphatidylethanolamine enriched on internal compartments [40].…”

A combined proteomic and genetic analysis identifies a role for the lipid desaturase Desat1 in starvation-induced autophagy in Drosophila

“…Phosphatidylethanolamine (PE) was shown to be the major phospholipid in Drosophila tissues, followed by phosphatidylcholine (PC) and phosphatidylinositol (PI), whereas phosphatidylserine (PS) constitutes only a minor portion of total fly lipids. 22 Thus, we focused on PE, PC and PI and analyzed lipid species containing Palmitic/Palmotoleic or stearic/oleic fatty acyl chains since palmitoyl-CoA and stearoyl-CoA are the preferred substrates of SCD. 23 Using multiple monitoring reaction based on headgroups and fatty acyl compositions of the lipid species, we detected a decrease in PC levels in Desat1 mutants and changes in the saturation profile of approach.…”

Ceramide Generation by the Reaper Protein Is Not Blocked by the Caspase Inhibitor, p35

“…During signaling in mammalian systems, ceramide is generated either by hydrolysis of sphingomyelin, mediated by sphingomyelinases, or, by de novo synthesis, mediated by ceramide synthase. Dipteran flies were previously noted to contain virtually no sphingomyelin but instead have ceramide phosphorylethanolamine (CPE), an analogous sphingolipid with a phosphoethanolamine head group rather than the phosphocholine found on sphingomyelin (60,61). In preliminary studies, we found that SL2 cells contain approximately 600 pmol of CPE/ 10 6 cells and undetectable levels of sphingomyelin.…”